Refrigerating apparatus



July 20, 1937. H. F. SMITH REFRIGERATING APPARATUS Original Filed Nov. 24, 1930 4 Sheets-Sheet l QMN m QAN ma Mm a a Q a e a O c c a a o d MN m SE a mm 2: w 1 Sm, i @N l llll 3 3w 2w p NS\ .2 QQx w m: mi \R\ a INVENTOR 3 W34 ATTORNEYS July 20, 1937. H. F. SMITH REFRIGERATING APPARATUS Original Filed Nov. 24, 1930 4 Sheets-Sheet 4 INVENTOR ATTORNEYS Patented July 20, 19 37 4 REFRIGERATING APPARATUS Harry F. Smith,YDayton, Ohio, assignor, by mesne assignments, to General Motors Corporation, a corporation of Delaware Application November 24, 1930, Serial No. 491,708

Renewed November 13, 1935 27 Claims. (01. cz-ize) This invention reates to refrigerating apparanected through conduit I64 to an evaporator E, tus and more par icularly to cooling units or which is supported within the food storage com-' evaporators for use in, refrigerating apparatus. partment I68of a refrigerator cabinet I54. The The invention is particularly adapted for use with generator-absorber I58 is both heated and cooled 5 the absorption type of refrigerating system but by a volatile fluid such as ethyl chloride confined 5 UNITEDSTATES PATENT OFFICE may also be used w'ith other types of systems esin a closed circuit which includes a vapor shell pecially' those employing an evaporator of the I10, which may be filled to the level I12, a vapor flooded type. condenser I14, cooled by a coil I90 and connected One of the objects of the present invention is to the vapor shell by a vapor-conduit 6-418, 10 to provide animprovedevaporator structure and and a liquid drain connection I80.

more particularly to provide an improved evapowhen the generator-absorber I58 is to be rator structure wherein the liquid refrigerant is heated, a burner I82 is'lighted and a Valve s caused to pass over an increased refrigerating closed in a valve chamber I86 connected between surface by forces generated within the evapora the conduit connections I16 and I18. The burner tor. vaporizes sufiicient liquid in the .vapor shell I10 15 A further object of this invention is to provide to force most of the liquid up into the condenser an improved evaporator'construction employing I14 through the conduit I80, reducing the level a liquid refrigerant reservoir wherein means are of liquid to I88. Thereafter liquid is vaporized provided for lifting the liquid refrigerant to a by the burner I82 and condensed on the genera- 2f) refrigerating surface above the level of liquid in tor-absorber I58 to heat the latter. Whenthe 20 the reservoir. v generator-absorber is to be cooled, the burner is A still further object is to provide an evaporaturned off and the valve I84 is opened. The tor for use in absorption machines, said evaporavapor in the shell I10 then flows up into the contor being so constructed and arranged that its "denser I14 and the liquid previously held in the refrigerating surfaces are at all times contacted d s r d s into the Shell Submerging by cold liquid refrigerant and wherein means are the generator-absorber I58. The hot generatorprovided for preventing the transfer of hot res ber V D G s q Vapor being frigerant into contact with the refrigerating surcondensed in the condenser I14 and returning as faces. 7 liquid through the conduit I80. i i Further objects and advantages of the present 30 invention will be -appa.rent from the following 'f description, reference being had to the accom- Water circulates continuously, P fi st panying drawings, wherein a preferred form of through the condenser coil I90, through the con-- the present invention i clearly shown, necting conduit I92, the condenser coil I62, and In the drawings: thence through a conduit I52 to a valve casing 5,

Fig. 1 is a front view of a cooling unit embody- 2 2 w h p s i t a t r e trainment pump ing the invention together with a diagrammatic aving a su t Chamber 1 d a t oat I96 illustration of the remaining elements in an ab through which a l Water s s a gedsorption refrigerating system; The valve casing 242, contains a throttle valve Fig. 2 is a vertical longitudinal sectional view which is Opened by a Spring 252 n Closed by 40 of th evaporator; a lever 246 actuated by a bellows 256 connected Fig. 3 is a sectional view along the line 3-3 of to e refrigerant c t 6 by a conduit 258. Fig v I v The jet pump tends constantly to produce a vac- 4 is ti l vi w along th i 4 4 f uum in the conduit I98 which is provided with a Figs. 2 and 3 with the insulation omitted; check valve I99 permitting flow of air in the di- Fig. 5 is a sectional view along the line 5-5 of rection of the jet p mp but preventing W 01' Fig. 6 of a modified form of applicant's invenwater in the reverse direction which might occur tion; and when the flow of water is too low to produce suc- Fig. 6 is a sectio 1 view along the lines 6-6 of tion. A bellows 200 is connected to the vacuum 5, j conduit I98 and operates the valve I84 by means 50 In Fig. 1 for illustrative purposes, there is of a lever 204, which includes forked arms 206 shown diagrammatically an intermittent absorppivoted at 208, and a central arm 2I0 extending tion refrigerating system including a generatorwithin the casing I86, the central .arm being absorber I58 which is connected by a. conduit I60 sealed to the casing by a packing bellows 2I2. to a condenser I56, cooled by a. coil I62, and con- The pivots 208 aremounted on a second forked 55 lever 2| 4, pivoted at 2I6, having its forked end surrounding the packing bellows 2I2 which latter may expand and contract against the force of the spring 220 in accordance with changes of pressure in the casing I86. The expansion of the packing bellows 2I2 depresses the lever 2 to raise an arm. Hi to remove a vacuum breaking valve 224 from a ported seat 226, and contraction of the packing bellows raises the arm 2I4 to permit the vacuum valve to close.

The supply of gas to the burner ,I82 is controlled by a valve 230 attached to a bellows 232, the interior of which is connected to the vacuum conduit I98. The vacuum conduit system includes a high temperature safety conduit 236, the end of which is closed by a fusible plug 240 disposed in a well in the vapor shell I10.

Operation of the system To start the apparatus, the pilot light 234 is lighted and water turned on in the conduit I92. At this time the generator-absorber is saturated with ammonia and the passages in the evaporator E are filled with liquid ammonia. The pressure within the 'vapor shell I10 is low, therefore the bellows 2i 2 is collapsed to close the vacuum valve 224. The vacuum established by the flow of water collapses the bellows 200 to close the vapor valve I84 and simultaneously collapses the bellows 232 to supply gas to the burner I82. The generator-absorber I58 is now heated as has been explained.

The generator-absorber I58 preferably, but not necessarily, contains a dry absorbent such as strontium chloride. The strontium chloride is rapidly heated by the ethyl chloride and after reaching a certain temperature the strontium chloride begins to distill ammonia which is con-v densed at a constant rate in the chamber I56 by the coolingwater. This maintains a substantially constant pressure in the ammonia circuit. Since the ammonia continuously absorbs its latent heat of evolution from the ethyl chloride within the shell I10, the ethyl chloride tends to remain at a constant pressure but when the evolution of ammonia ceases, the pressure of the ethyl chloride suddenly rises. When the pressure corresponding to the tension to which the spring 220 has been set is attained, the bellows 2I2 has expanded sufilciently to open the vacuum valve 224, permitting the gas valve 230 to close and the vapor valve I84 to be opened. This stops the heating period.

Opening of the valve I84 permits circulation of the ethyl chloride which cools the generatorabsorber as has been explained, the ethyl chloride being condensed by the cold water in the coil I and its pressure rapidly reduced. Likewise, the sudden immersion of the generatorabsorber in cold liquid reduces the pressure of ammonia. At this low pressure, the strontium chloride within the generator-absorber I58 absorbsammonia and produces refrigeration in a well-known manner in the evaporator E1 The latent heat of absorption of ammonia is removed by the ethyl chloride which is continuously vaporized on the shell I10 and condensed in the chamber I14. Refrigeration is carried on at a substantially constant temperature because the bellows 256 positions the water valve 244 in response to the temperature of the evaporator and thus regulates the flow of cooling water to maintain a rate of absorption which is in exact accordance with the refrigerating demand, or

closes the valve to stop the apparatus when no refrigeration is required.

The valve 244, for maintaining a constant temperature within the cabinet,-can be adjusted by jet pump to collapse the two bellows 200 and 232 and thereafter air will not be admitted fast enough to destroy the vacuum necessary to maintain ,the two bellows collapsed. This arrangement is for the purpose of admitting a small quantity of air in the jet chamber I94 in order that the air may continuously be removed from the chamber by the jet and thus keep the jet sufficiently agitated to maintain a sealing contact with the throat.

As the pressure of ethyl chloride is reduced,

If the generator-absorber should become overv heated for any reason, for example due to leakage of ethyl chloride from the vapor circuit, the fusible plug I40 will melt to destroy the vacuum and shut oif the burner'before a dangerous temperature can be reached. In fact heating'of the apparatus depends entirely on the assistance of a vacuum which in turn depends both on predetermined flow of cooling water and an intake condition of the controlcircuit. Therefore, unless cooling water is actually flowing at a. sufficient rate to condense the ammonia the burner cannot be lighted. Furthermore, breakage, leakage or failure of any part of the control circuit will break the vacuum to prevent Operation of the apparatus.

Difiiculty has been encountered in the use of absorption machines of the intermittent type due to the fact that the level of the liquid refrigerant within the evaporator changes between rather wide limits. For instance at the end of the absorption period or at the beginning of the heating period, there is practically no liquid refrigerant within the evaporator .while at the end of the heating period the evaporator is substantially filled with liquid refrigerant. Such a fluctuating level 01' refrigerant decreases the efficiency of the apparatus since hot gaseous and liquid refrigerant is brought in contact with the refrigerating surfaces during the generating period.

To overcome these disadvantages, I so con-, struct my improved evaporator that the refrigerating surfaces thereof areat all times, both during the absorption and generating cycles, in contact with relatively cold liquid refrigerant. This is accomplished in my improved construction by stopping the absorption period and starting the heating'or generating cycle while a con-- mains in the evaporator.

siderable quantity of liquid refrigerant still re- This is also accomplished by utilizing forces generated within the evaporator itself for forcing the liquid refrigerant onto the refrigerating surfaces, these forces being generated only during the absorption period.

In one embodiment of the evaporator E, shown in Figs. 2, 3 and 4, there is shown the tank member 40 which is positioned between the upper sides of the U-shaped plate-type heat absorption member 4| as is more clearly shown in Fig. 4. This heat absorbing member is formed of two'sheets or plates of metal 50 and 5| preferably stainless steel, each having a plurality of impervious cup-shapeddepressions and cor-' responding projections formed therein, the outer i plate 5| having depressions of greater depth forming projections which fit-into the opposite depressions in the inner plate 50. These'depressions extend over the greater portion of the bottom and side surfaces of the heat absorbing member 4|, but these depressions are omitted at the corners of the U-shaped member 4|, as shown at 48, as well as at the top of the sides indicated at 49.

The inner plate 50, near the top of its sides, has two longitudinal depressions 44 therein, one on either side, and also has a pair of opposite semi-spherical depressions 45 in the center of the long depressions 44. The outer sheet 5| has a bulge 45 on either side opposite the semispherical depression 45 on the inner sheet for absorbing the expansion due to welding. The sheets are made'first by forming the depressions 4 therein, and putting 'the sheets together in and projections of the adjacent sheets as well as passages 48 at the lower corners of the' U- ,with the passages 41.

and depressions prevent warping of the sheets proper relation which is facilitated by the fact that the projections of the outer sheet fit within the adjacent depressions. of the inner sheet. The sheets are then welded together around their edges and at the centers of the inter-engaging projections and depressions and then the assembled sheets are bent upward to form the U-shape of the member. By this form of construction a plurality of connected refrigerant passages 41 are formed between the depressions shaped member and along the passages 49 which form headersat the upper portions of the U- shaped, member extending to the front and rear of the unit and which headers communicate The opposite projections during welding. I

This type of wall structure has a number of advantages over the older types of wall structure. One of these advantages is the fact that with this structure a much narrower refrigerant space can be obtained and thus a lesser amount of-refrigerant is required to fill the refrigerant walls and consequently a lesser amount of refrigerant reason the wall structure itself isnot distorted.

Another advantage of this structure is thatthenested construction facilitates the welding operation since it holds the sheets-together in.

proper relation during the welding operation and prevents them from slipping. Upon the completion of the welding operation the nested contions on the inner sheet 50 is used as a tray support for shelf 52 which supports the upper tray. This tray support shelf is formed of a pair of sheets 53 and 54 each having impervious cupshaped projections and corresponding depressions formed within. The projections on the lower sheet are longer than the projections on the upper sheet 53 and fit into the depressions formed in the upper sheet 53. The upper sheet 53 is continuedbeyond the side edges of the lower sheet 54 and is bent upwardly and outwardly on either side, as shown at 55, and fits between the third and fourth row of projections 43 on the inner sheet 50 of the U-shaped member 4|. The refrigerant passages 56 are formed about the projections of the sheet 54 between the sheets 53 and 54. The edges of the sheets are welded together to enclose the refrigerant passages. The bottom of the U- shaped member 4| serves asga second tray supporting shelf.

The liquid supply reservoir or tank 40 is positioned above the tray supporting .shelf 52 between the two sides of the U-shaped member 4|. A duct 5! depends from the rear end of the tank member 40 and extends straight downwardly, passing through the tray support shelf 52 as shown at 58, and then makes a reverse turn 59 which forms a trap portion and finally enters the tray supporting. shelf from thebottom as shown at 60. To one side of the duct 51 another ,duct 63, of a relatively small size, extends upthereof. The duct 68 extends from one side of the distributing member 64 and enters the top portion of the tank member 40. This duct 68 conducts gaseous refrigerant from the distributing member 64 to the tank member 40. The duct 69 extends forwardly from the distributing member 64 and is connected to the duct 10 which passes over the tank member and connects the opposite semi-spherical depressions 45 in the upper portion of the inner sheet 50 of the U-shaped member 4|. This duct 69 conducts liquid refrigerant from the distributing member 64 to the U-shaped member 4| through the duct I0 the bulges 45 and the long passages or headers 49 on one side of the unit.

The duct 1| connects into the front end of the tank member 40 and extends rearwardly therefrom alongside of the tank member 40 to the rear of this portion and then is bent downwardly around the tank where it connects to duct 2 shown in Fig. 2 which passes out the rear of the evaporator as shown at 12. This duct forms a connection between the evaporator and the remaining units of the absorption system shown in Fig. 1.

Separating the tank member 40 from the upper ice tray compartment 15 is an L-shaped sheet metal shield 16 which also forms the rear wall of U-shaped member 4|.

these compartments. This shield 16 has its edges bent up as shown 'at which are so formed as to rest upon a horizontal row of projections on the inner sheet member 50. At its lower end is flange 18 (Fig. 2) which rests upon the bottom ofthe U-shaped member 4|. The tank member 48 is enclosed at the top by the supporting member 80 which fits between the sides of the U-shaped member and has its edges bent up and turned inwardly as shown at 8| so that it may be secured to the top of the compartment within the refrigerator as shown at 82. This bracket 80 is welded at its outer sides to the top edges of the The tank member 40 is enclosed at its rear and front by sheet metal members 83 and 84. A valve shut-off screw 85 which screws into the front end of .the tank member 40 projects: directly through this front member 84. Within this enclosure about the tank member 48, granulated cork 86 is placed so that the tank member may be insulated as far as possible from the food storage compartment of the refrigerator as well as the remainder of the evaporator.

A shield 81 is fitted to the front end of the evaporator and is secured thereto by long bolts 88 which are fastened at the rear end to the closure piece 89 which in turn abuts against the rear portion of the shield 16 and the rear end of the U-shaped member 4|. These long bolts support a shelf 9| which has its adjacent side curled about one of these long bolts 88 as shown at 9|]. This shelf at its other side may be supported by stud projecting from the adjacent side wall of the refrigerator and may be used to support milk, cold beverages, and other food products.

In assembling, the tank member 40, the supporting shelf 52, and the rear end of the distributing member 64 and connecting ducts, as

heretofore described are assembled independently the front and rear portions 66 and 61 of distributing member 64. The space between the enclosure and the tank member 48 is then packed with granulated cork. It will thus be seen that a novel and easy method of assembly. is provided.

When this evaporator is used with an intermittent absorption type of refrigerating system, the level of the liquid refrigerant in the tank portion of the evaporator fluctuates with the changing cycles. I, however, have constructed this improved evaporator so that liquid refrigerant is kept in contact at 'all times with, the refrigerant surfaces regardless of the fluctuation of the level of liquid refrigerant within the reservoir or tank portion of the evaporator.

In the improved unit, ice trays 8| are placed upon the shelf 52 and the bottom portion of the U-shaped member 4|. The liquid within the evaporator seeks its own level and fills the duct 51, the passages in the shelf 52, and the lower portion of the connecting duct 53. Heat absorbed from the ice trays causes the evaporation of some of the. liquid refrigerant in the shelf 52. This evaporated gaseous refrigerant is prevented from returning directly to the tank member 48 by reason of the trap portion 59 in the duct 51. Therefore it must ascend through connecting duct 63 and in doing so bubbles upwardly through this duct and carries liquid refrigerant along with it, similarly to the action of an air lift pump, on up to the top bend of the duct 63 where the refrigerant overflows into the distributing member 84.

This vapor lift action takes place because the mixed column of vapor and liquid refrigerant is lighter than the solid column of liquid refrigerant of lesser height. The upper end 65 of the duct 63 is bent forwardly so as to direct refrigerant away from the gas duct 68. From this point the gas-.

e ous refrigerant separates from the liquid refrigerant and passes back to the tank member 40 through the duct 68. g The liquid refrigerant, however, collects in the bottom of the distributing member 64 and flows out therefrom through the duct 69 to the duct lll'and into the passages between the inner and outer sheets 50 and 5| ofthe heat absorbing member or refrigerating surfaces 4|. The distributing member 64 together with the ducts 65 and '68 forms a trap for preventing the flow of liquid refrigerant from the passages between the inner and outer sheets 58 and 5| back to the ice tray shelf 52. The duct 68 acts as an overflowing device for liquid refrigerant within the distributing member. The duct 58, distributing member 84 and pipe 69 serve as a means for conducting evaporated or gaseous refrigerant, from the refrigerated surfaces 4| through headers 49, bulges'45 and conduit 18, back to the refrigerant circulating unit. If the liquid refrigerant within the distributing member should rise above the duct 68, the excess of liquid refrigerant will flow back into the supply reservoir. This vapor lift action carries a sufficient amount of refrigerant to fill the passages within the heat absorbing member 4|. It will be seen that this member 4| is t-huskept filled with liquid refrigerant and isthus sealed to prevent gaseous re-. frigerant which might have access thereto through the upper connectingducts from the tank member 40. It has been found that there is suflicient heat absorbed from various other sources to produce enough boiling to keep the U-shaped absorbing member substantially filled even when the ice trays have not been in use for a considerable length of time. be seen that an evaporator has been provided whose refrigerating surfaces are at all times in contact with cold liquid refrigerant. Thus during the heating or generating period, hot refrigerant cannot contact these cold surfaces.

In the modification hown in Figs. 5 and 6, v

ing the major portion of the cooling surfaces at the top portion of the brine and above the tank portion of the unit. This also improves circulation of the brine within the brine tank since the cold brine will move to the bottom of the tank to be warmed there and will then rise to the top of From this it will In my improved construction the cooling unit is'inserted into the brine tank I00. Adjacent the large aperture in a wall of the tank a re-enforcing ring member IN is fitted in the interior of the tank adjacent the aperture and a heavy supporting plate I02 is fit to the outside of the wall of the tank adjacent the aperture. Studs I03 pass through the supporting plate I02, the wall of the brine tank, and the supporting member IM and fastens these members together. The tank member I04 is fitted within the aperture in-the supporting plate I02 and has its rear portion extending rearwardly therefrom inside the brine tank and its front portion extending forwardly outside the brine tank. A shield I05 surrounds the entire portion of the tank member within the brine tank, enclosing an insulating space there- I about containing a suitable insulating material such as cork for'preventing thermal contact between the brine and the tank member.

The tank member I04 is closed by a rear cap I06. On the lower portion of this cap a large duct I91 extends downwardly through the bottom of the shield I05 into the brine. This duct is closed by a plug I08 at its lower end. A pair of ducts I09 are connected to the duct I01 adjacent its lower end and project upwardly to the heat absorbing portion I I of the evaporator. Fins I I I are fastened along the lower ends of these connecting ducts I09 for a purpose which is to be.

- tion somewhat similar to a key hole. These ducts are connected at the front end by a cross duct I I3.

and areprovided with fins III! which increase the area of heat transfer between these ducts and brine in the top portion of the tank: A duct I I1 returns gaseous refrigerant from the refrigerant ducts H2 to the tank member I04.

Refrigerant is supplied to the tank member I04 through the connection H5. and the conduit IIG, which extends upwardly into a dome similar to a steam dome of a steam boiler in'the top portion of the tank member I04. The refrigerant fills the major portion of the tank member during the heating period of the cycle and a smaller portion during the cooling portion of the cycle. Refrigerant flows downwardly through the duct I01 and then divides and turns upwardly into the ducts I09 from which the refrigerant absorbs a evaporates, collects in the top portion of these ducts and is removed to the tank member I04 through the duct II1.

Thus there is shown how I am able to supply liquid refrigerant to the heat absorbing member at the top portion'of the brine tank and above the tank portion of the evaporator. It will be seen that the invention is not merely limited to an evaporator-for the absorption type of refrigerating system but is also adapted to the flooded type of evaporator as well as other types. All that is necessary is to supply a float member, needle valve, and inlet and outlet ports to the tank member to convert the evaporator shown to the flooded type of evaporator often used with the condenser-compressor-expander type of refrigerating system. The liquid in this flooded type circulates in a similar manner as that described with the absorption type of apparatus.

While the form of embodiment of .the invention as herein described, constitutes a preferred form, it is to be understood that other .forms might be adopted, all coming within the scope of the claims which follow.

. rectangular sheet member ,having a. plurality of impervious depressions and corresponding projections formed therein, a second sheet member having a plurality of impervious depressions and corresponding projections formed therein, said projections of said second sheet member extending into said depressions in said first mentioned sheet member forming a refrigerant space between the sheets surrounding said depressions, said sheet members being bonded together at the bottom portions oftsaid depressions and sealed at the edges to enclose the refrigerant space.

- 3. A cooling unit including a liquid refrigerant supply reservoir, a U-shaped plate type refrigerating surface beneath the supply reservoir, en-

closing a freezing chamber, said U-shaped plate type refrigerating surface comprising a pair of sheet metal members each having a. plurality of depressions, and corresponding projections formed therein, the projections of one sheet extending into the depressions of the other sheet and spacing the portions of the sheets surrounding the depressions and forming a narrow refrigerant space thereby, said sheets being sealed at their edges enclosing the refrigerant space, an ice tray shelf supported between the walls of said U- shaped refrigerating surface within said freezing chamber, and means for supplying said refrigerant space in said U-shaped refrigerating surervoir.

"4. A plate type-refrigerating element comprising a sheet member having a portion with a plurality of impervious depressions therein, a second sheet member having a portion with a plurality of impervious depressions and corresponding projections formed therein extending into and nesting into the depressions in the first mentioned sheet member, the portions of the sheets surrounding'each of the depressions being spaced from each other andforming a refrigerant space between said sheet members,fsaid portions of the sheets surrounding the depressions being sealed together adjacent their perimeters for-enclosing face with liquid refrigerant from the supply resthe refrigerant space, said sheets also being bond-.

red together at the central portions of the depressions and corresponding projections.

5. A plate'type refrigerating element comprising a sheet member having a portion with a plurality of impervious depressions and correspondpervious depressions and corresponding projec tions formed therein, said projections in said second sheet member extending into the depressions of the first mentioned sheet member, said projections in said second sheet member having a greater height than the depth of the depressions in said first mentioned sheet member for providing a refrigerant space between the portions of said sheet members surrounding each of said depressions, the edges. of said sheets being sealed for enclosing said refrigerant space, the end portions of the projections of the second sheet contacting the bottom portions of the depressions of the first sheet.

6. A plate type refrigerating element comprising a sheet member having a portion with a plurality of depressions and corresponding projections formed therein, a second sheet member having a portion with a plurality of depressions and corresponding projections formed. therein, said projections in said second sheet member extending into and being formed to fit into the depressions of the first mentioned sheet member, said projections in said second sheet member having a greater height than the depth of the depres-. sions in said first mentioned sheet member for providing a refrigerant space between the portions of said sheet members surroundingeach of said depressions, the edges of said sheets being sealed for enclosing said refrigerant space, the central portions of the interengaging projections and depressions being bonded together to hold the sheet members in proper spaced relation 7. A plate type refrigerating unit, comprising a sheet member having a plurality of cup-shaped depressions therein, a second sheet member havsions therein, a second sheet member having a plurality of cup-shaped depressions and corresponding projections formed therein, said projections extending into and being formed to fit into the cup-shaped, depressions inv said first mentioned sheet member, said projections, in said second sheet member having a greater height than the depth'of the depressions in said first mentioned sheet member for forming a refrigerating space between the sheet'members, the interengaging cup-shaped projections and depressions being bonded together to hold the sheet members in spaced relation.

9. A plate type refrigerating unit, comprising a sheet member having a plurality of cup-shaped depressions therein-a second sheet member hav-' ing a plurality of cup-shaped depressions and corresponding projections formed therein, said projections extending into and being formed to fit into the cup shaped depressions in said first mentioned sheet member, said projectionsin said. second sheet member having a greater height than the depth of the depressions in said first mentioned sheet member for forming a refrigerating space between the sheet members, the interengaging cup-shaped projections and depressions and the edges of the. sheets being bonded together to form a refrigerant container,

10. A plate type refrigerating unit comprising a sheet member having a plurality of cup-shaped depressions and corresponding projections therein, a second sheet member having a plurality of cup-shaped depressions and corresponding projections therein, the projections of-said second sheet member extending into the depressions of said first mentioned sheet member, said projections .in said second sheet member having a greater height than the depth of the depressions in the first mentioned sheet member spacing the portions of said sheet members surrounding each of said depressions and forming a refrigerant space therebetween.

11. A cooling unit comprising generally fiat outer sheet metal walls bent partially around a freezing chamber, some of said walls being formed of a plurality of spaced sheets of metal, each of said spaced sheets having a plurality of depressions and corresponding projections formed therein, the projections of one of the sheets extending into and abutting the depressions of the adjacent sheet, spacing the portions of the sheets surrounding the depressions and forming a space therebetween.

12. A cooling unit comprising generally fiat outer sheet metal walls bent partially around a freezing chamber, some of said walls being formed of a plurality of spaced sheets ofmetal, each of said spaced sheets having a plurality of depressions and corresponding projections formed therein. the projections of one of the sheets extending into the depressions of the adjacent sheet, spacing the portions 01' the sheets sur- -rounding the depressions and forming a space therebetween, said sheets being bonded together at the bottoms of their projections.

13. A cooling unit comprising generally flat outer sheet metal walls bent partially around a freezing chamber, some of said walls being formed of a plurality of spaced sheets of metal, each of said spaced sheets having a plurality of depressions and corresponding projections formed therein, the projections of. one of the sheets extending into the depressions of the adjacent sheet, spacing the portions of the sheets surrounding the depressions and forming a space therebetween and an ice tray shelf supported between said walls within the freezing chamber,

said ice tray shelf comprising a plurality of sheets of metal bonded together at-their edges, at least one of the sheets being deformed to provide refrigerant passages between the sheets, and duct means connecting the spaces between the sheets of the outer sheet metal walls and the refrigerant passages in the ice tray shelf.

14. A cooling unit including a plurality of spaced sheets of metal extending around the bottom and the sides of a freezing chamber and forming a double walled U-shaped structure, each of said spaced sheets having a plurality of depressions and corresponding projections formed therein, the projections of one of the sheets extending into and abutting the depressions of the adjacent sheet, spacing the portions of the sheets surrounding the depressionsand forming a refrigerant-space therebetween.

15. An evaporator comprising a plurality of sheets of metal fastened-and sealed together at their edges and having 'end portions bent up to form a generally U-shaped structure having vertical side walls terminating at the upper ends with sealed edges, said sheets of metal being separated adjacent the upper edges along the top of the vertical walls of the U-shaped structure to form a longitudinal passage on each side,

said sheets being also spaced to provide a plurality of refrigerant passages extending between the sheets from one of the longitudinal passages to the other, an ice tray shelf supported between the sides of the U-shaped structure, said shelf including sheet-like portions spaced apart at cer; tain points and secured together at certain other points to form a refrigerant expansion passage therebetween, and means for conducting refrigerant to said expansion passage in said shelf and to the refrigerant passages between the sheets of the U-shaped structure.

16. An evaporator comprising a U-shaped structure having a pair of vertical wall portions connected at their lower ends formed of a plurality of sheets of metal fastened together and sealed at their edges, said vertical wall portions terminating at their upper ends with sealed edges, said sheets being deformed to provide refrigerant passages between the sheets extending from the upper portion of one of the sides'of the U-shaped structure down across -thebottom portion and up the other side thereof, said sheets being bonded together between the passages, said sheets being also deformed'to provide longitudinal passages connecting the ends of the refrig erant passages extending from one side to the other, a cross'duct extending from one longituedges, said sheets being deformed to provide dinal passage directly to the other longitudinal passage, an ice tray shelf supported between the sides of the U-shaped structure, said shelf including sheet-like portions spaced apart at certain points and secured together at certain other points to form a refrigerant expansion passage therebetween, and means for conducting refrig-. erant to said expansion passage in said shelf and to the refrigerant passages between the sheets of the U-shaped structure. 1

17. An evaporator comprising a U-shaped' structure having a pair of vertical wall portions connected at their lower ends and formed of a plurality of sheets of metal .fastened together and sealed at their edges, said vertical wall portions terminating at their upper ends with sealed refrigerant passages between the sheets extending from the upper portion of one of the sides of the U-shaped structure down across the bottom the U-shaped structure, an. ice tray shelf sup-' ported upon 'said projections, said shelf'including sheet-like portions spaced apart at certain points and secured together at certain other points to form a refrigerant expansion passage therebetween, and means for conducting refrigerant to said expansion passage in said shelf and to the refrigerant passages between the sheets of the 'U-shaped structure. a a

18. An' evaporator comprising a U-shaped structure having a pair of vertical wall portions connected at their lower ends formed of a plurality of sheets of metal fastened together and sealed at their edges, said vertical wall portions terminatingfat their upper ends with sealed edges, said sheets beingdeformed to provide refrigerant passages between the sheets extending from, the upper portionof one of the sides of the U-shaped structure down across the bottom portion and up the other side thereof, said sheets being bonded'together between the passages, said sheets being also deformed to provide longitudinal passages connecting the ends of the refrigerant passages extending from one side to the other, an ice tray shelf comprising a plurality of sheets of metal fastened and sealed together'at their edges and being deformed to provide refrigerant passages between the sheets, said ice tray shelfbeing supported between the vertical wall portions of the U-shaped structure, means for conducting liquid refrigerant to the ice tray shelf, means for conducting liquid refrigerant from the ice tray shelf to the passages in the U-shaped structure.

19. An evaporator comprising a U-shaped structure having a pair of vertical wall portions connected at their-lower ends formed of a-plurality of sheets of metal fastened together and 'sealed at their edges, said vertical wall portions terminating, at their upper ends with sealed nal passages connecting the ends of the refrigerant passages extending from one side' to the other, an ice tray shelf comprising a plurality of sheets of metal fastened and sealed together at their edges and being deformed to provide refrigerantpassages between the sheets, said ice tray shelf being supported between the vertical wall portions of. the U-shaped structure, means for conducting liquid refrigerant tothe ice tray shelf,

means for conducting liquid refrigerantfrom the ice tray shelf to the passages in the U-shaped structure, and means for conducting vaporized refrigerant from the longitudinal passages at the top of the vertical wall portions.

20. A sheet metal evaporator for refrigerating apparatus comprising, sheet-like portions secured together at certain points and being spaced apart at certain other points to form refrigerant passages therebetween, said sheet-like portions being bent to form at least three walls of asharp freezing compartment and providing said evapadapted to flow thereover, ashelf disposed within said sharp freezing compartment for supporting ment, means for supplying refrigerant to the refrigerant passage in said shelf, and means for conducting refrigerant from the shelf to the refrigerant passages in said walls. 21. A sheet metal evaporator for refrigerating apparatus comprising, sheet-like portions secured together-at certain points and being spaced apart at certain other points to, form refrigerant passages tl'ierebetween,- said sheet-like portions being bent to form two vertical side walls and a horizontal wall of a sharp freezing compartment,

in, said shelf including sheet-like portions secured together at certain points and being spaced apart at certain other points to form a refrigerant passage therebetween, said sheet-like portions of. said shelf being formed separate from and independent of the sheet-like portions of the walls of the freezing compartment, means for supplying refrigerant to the refrigerant passage in said shelf, and means for conducting refrigerant from the shelf to the refrigerant passages in said walls.

at certain other points to form a refrigerant pasage therebetween, said sheet-like portions of said shelf being formed separate from and independent of the sheet-like portions of the walls of the freezing compartment, means for supplying refrigerant to the refrigerant passage in said shelf,

and meansfor conducting refrigerant from the shelf to the refrigerant passages in said Walls.

23. An evaporator for refrigerating apparatus comprising, sheet metal portions cooperating with one another to provide a refrigerant passage therebetween, said cooperating sheet metal portions being arranged to form at least three impervious walls .of a sharp freezing chamber and being exposed to air adapted to flow over said evaporator for cooling said air, arefrigerated shelf within said sharp freezing chamber for supporting areceptacle therein and for dividing said chamber into a plurality of compartments,

means for conveying refrigerant from a source of supply directly to said shelf, and means for conducting refrigerant. from the shelf into direct contact with the air cooling portion of the evaporator. f

24. A cooling unit for a refrigerating system including an evaporator comprising a U-shaped refrigerant circulating air cooling portion and a header at each end of the legs of said portion, each of said headers being in communication with one another, means forming a refrigerant conduit and providing a shelf horizontallydisposed between the legs of said U-shaped portion, means for admitting refrigerant to said conduit, means providing communication between said conduit and said air cooling portion of said evaporator, and means for withdrawing refrigerant from said evaporator.

25. An evaporator for a refrigerating system comprising, superimposed outer and inner sheet metal portions secured together and arranged to form the side walls and a bottom wall of a freezing chamber, depressions formed in at least one of said sheet metal portions and extending parallel to and being spaced from the ends of said.

one of said sheet metal portions and also spaced from the front and back edges of said sheet metal portion, said depressions cooperating with the zontally disposed between the side walls of the freezing chamber and dividing said chamber into a plurality of compartments, means for supplying refrigerant to said conduit, means pro-,

viding communication between said conduit and the refrigerant passages. in the walls of said freezing chamber, and means for Withdrawing refrigerant from said evaporator.

26. A sheet, metal evaporator comprising an outer one piece shell and an inner one piece shell bent to form a sharp freezing chamber, an embossed portion in one shell consisting of an arcuate depression spaced from an edge of the shells and. cooperating with the other shelhto form a header, an embossed portion in one shell spaced from a different edge of said shells and consisting of an arcuate depression cooperating with the other shell to form another header, em-

bossed portions in one shell and forming refrigerant passageways leading from-the headers and extending over the exposed surface of the shell forming the sharp freezing chamber, said headers being completely confined within the edges of said shells, a substantially continuous weld around the periphery of the shells to completely seal the evaporator with the exception of inlet and outlet connections, means forming a refrigerant conduit and providing a tray supporting shelf horizontally disposed within said freezing chamber and dividing the interior thereof into a plurality of compartments, and connecting means for maintaining a common refrigerant level in both headers.

27. An evaporator for a refrigerating system comprising, superimposed outer and inner sheet metal portions secured together and having their ends spaced apart to form a u -shaped structure defining walls of a sharp freezing chamber, depressions formed in at least one of said sheet metal portions and extending along and being spaced from the ends of said one of said sheet metal portions and also spaced from the front and back edges thereof, said depressions cooperating with the other of said superimposed sheet metal portions to form headers located adjacent the ends of the legs of the U-shaped structure, said headers being opposed due to the U-form of the evaporator structure, embossed portions in at least one of said sheet metal portions providing passages leading fromtheheaders and extending over the legs and their connecting yoke portion of the structure, a conduit extending between and having its ends connected with said headers for maintaining a common refrigerant level in said 

